Not only that, but also that it's a giant scam. Because if that is the case, even at a probability as low as 0.1%, valuable resources would be wasted that could be used to mitigate other existential risks, or being used by someone who follows selfish motives.

You say that as if it's worse than other ways that money could go to waste.

(There are good game-theoretic reasons to act sort of as if you thought that, but they should be made explicit, and explicit consideration of them probably wasn't what motivated your statement.)